After my commit	1e063e8b "optimise references list handling in
OWeakConnectionPoint"

Reduce scope of locking, and copy a the performance trick from
OInterfaceContainerHelper.

Change-Id: Idc218e9d4edf45f8c37c7e517d1a26821800448b
Reviewed-on: https://gerrit.libreoffice.org/25406Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Michael Stahl <mstahl@redhat.com>